1. Field of the Invention
The invention relates to a moving body control system that performs drive control based on self-posture information, a moving body control method, and a non-transitory computer readable medium in which a control program is stored.
2. Description of Related Art
In recent years, technologies for controlling travel motion and posture of a coaxial two-wheel vehicle by detecting self-posture information, using a gyro sensor, an acceleration sensor, etc., and controlling a drive motor or motors provided in the coaxial two-wheel vehicle, based on the detected posture information, have been developed. In this type of coaxial two-wheel vehicle, the self-posture information is detected based on signals from the gyro sensor and acceleration sensor, and a rotation command to the motor(s) is computed so that the vehicle can maintain its own posture, according to the principle of posture control using an inverted pendulum, or the principle of ZMP (zero moment point) control for two-legged robots. Then, rotation command data thus obtained is transmitted to a motor control device. Thus, the two-wheel vehicle is able to travel due to changes in the center of gravity or posture of a vehicle rider, while maintaining its own posture through the above feedback control.
The above-described coaxial two-wheel vehicle is unstable in its front-back direction because of its structure, and the posture is stabilized by performing drive control on the wheels based on feedback from a posture sensor. Also, vehicle operations, such as forward and backward travelling, and right and left turns, are performed according to a command provided by shift of the center of gravity of the rider, a command provided by inclination of a step or steps, a command from a control bar, or the like. In other cases, the coaxial two-wheel vehicle may be remotely operated according to a command entered from the outside, or may make autonomous movements based on its own trajectory planning.
However, in a known control system of the coaxial two-wheel vehicle, it requires substantial time to perform arithmetic processing for detection of the posture. Therefore, a quick-response posture sensor and a controller (CPU (Central Processing Unit)) having high computing power are needed, so as to achieve a fast control cycle while keeping sufficient control performance. Namely, an expensive system (including CPU and posture sensor) is supposed to be used, resulting in an increased cost. If, on the other hand, an inexpensive system is employed, the control cycle slows, and a control gain(s) cannot be increased, resulting in deterioration of the performance. Therefore, a method that enables an inexpensive system to achieve a fast control cycle while keeping sufficient control performance is strongly desired.
In the meantime, an inverted two-wheel vehicle is known (see, for example, Japanese Patent Application Publication No. 2010-030436 (JP 2010-030436 A)) in which a torque command for motors is produced based on a driving velocity command based on posture information and detected driving velocities of the wheels to drive the motors.
When the inverted two-wheel vehicle travels based on a constant velocity command while being inclined by a certain angle in the travelling direction, for example, the inverted two-wheel vehicle makes uniform or constant-velocity motion, and cannot provide the inertial force that corrects the inclination of the inverted two-wheel vehicle; therefore, the vehicle rider has to perform a cumbersome operation or movement to raise the posture up.